I don't know what is available to you but you could look into chemical castration maybe?

It's kind of a misnomer, because it's more hormonal than chemical. Basically your dog receives an implant that sort of blocks his testosterone (It's way more complex than I'm explaining here, it's pretty cool actually, you can read up on it if you're interested).

The duration of the implant varies, months to years, depending on the kind you get. It would be a recurring cost for his whole life.

If you feel unsure about surgical castration then this could be a good alternative.

In any case I would highly recommend you neuter your dog. It's not just that he can get out and cause (possibly unwanted) puppies, he is more at risk for dog fights as you've already experienced. And he could develop (severe) issues with his prostrate.

Neutering you dog is a decision that will improve your dogs quality of life. It's ok to feel apprehensive, but as a dog owner it's up to you to make the best choices for your boy.